These providers operate across multiple platforms and share intelligence about suspicious behavior, including arbitrage patterns. If you’re taking one side of a market on one site and the opposite on another — they see both sides. 
It’s normal for them to become aggressive because all this bookie will suffer shared losses if they allow continuous arbitrage betting due to +EV on every bets.
This is a huge amount of loss from all of them if there’s a bunch of user doing this method on large scale bet. As business, they will not allow a guaranteed profit because their operations profit will be affected.
They would suffer some small losses, but overall they are still printing an insane amount of money.
The very small amount of EV gained by sharps is absolutely miniscule compared to the losses of casino players and rec sports bettors.
It's literally like a drop in the ocean for these bigger companies, they can also manage their risk accordingly and cut users off (without stealing funds ofc).